Method of manufacturing molded bodies



loo. couPosnlous, I

COATING R PLASTIC- CFOSS Reference Examme' latented July 30, 1940 I y METHOD OF MANUFACTURING MOLDED BODIES .:.l Albert A. Fowler, North Hollywood, and Russell M. Otis, Pasadena, Calif.

No Drawing. Application December 18, 1936,

' Serial No. 116,643

4 Claims. (C1. 18-475) This invention relates to the methods of A preferred form of molded body employs manufacture of molded bodies in which the granular spumiform material in which a pitchy l molded bodies are formed of light-weight parsubstancesuchasasphaltisdistrlbuted uniformly ticles of spumiform structure which are bonded throughout each granule and exists on the extogether. tex'iors of the granules. The method of making I In our patent, No. 2,038,034, we disclosed a Such a spumiform material is set forth in detail 5 material composed of a solidified silicate having in our oopending application above referred to.

a spulniform structure, that is, a bubbled or Briefiy,inthemakingof thisgranular spumiform intumesced solidified material having a strucmaterial a thick water solution is formed of an 19 ture similar to that of foam. Among others, a intumesoent material such as alkaline silicate, or n granular form of this material was disclosed. In tetraborate, or a composition of alkaline an application, Ser. No. 116,644, filed by us conoxide, boric oxide. and silicon dioxide, and to cln'rently with the present application, we disthis thick solution is preferably added a pitchy closed a glass-like material or spumiform strucsubstance, such as asphalt and mixed therein :0 ture including in its composition alkaline oxide, while being heated. This compositionispartially boric acid, and silicon dioxide, which was also desiccated by heat to a degree that when cold adaptable to a granular form. In another 942- it is a hydrous solid. This solid is preferably plication, Ser. No. 116,642, filed by us concurcomminuted into particles of small size which rently with the present application, we disclosed are then rapidly heated to cause lntumescence g a light-weight glass-like material of spumiiorm In this intumescing stage the granules 19 structure of composition having included, with expwd many times and term a lightweight, a pitchy water-repellent substance, an intumeswater-repellent granular spumiform material cent material which was stated in one composiwith pitch through and through. In making this if tion to be alkaline silicate; in another, sodium type of material for use in molded bodies as g5 tetraborate; and in another, alkaline oln'de, boric herein described. we pret r t p y. as p tch.

UNITED STATES PATENT ()FFICE oxide, and silicon dioxide. These spumiiorm an asphalt of high penetration (100-250), and

materials were also disclosed in granular form. we the asphalt in the propor ion or 11 to An object of this invention is, by bonding toparts by weight of halt to 1004mm! of the gather spumiiorm materials similar to those other lnumescent solid content). We

I o above-mentioned, to provide a light-weight may my e). a ur or artificial asphalts, l molded body which is possessed all good heat ind of artificial 9 1 th r s m refined I sulating properties. Another object of our .inore-1r blown. o t t made by any other process. vention is to provide a light molded body which or we may employ asphalt in the form of a water is water-repellent. Still another object is to emulsion. We may also employ other pitches l provide eficient methods of making these molded such as coal tar pitch, and pitch derived from a bodies. either animal or vegetable matter, and in our The granular or pulverulent spumiform mateu Of th W d vin in W 1188 it -in its rial which is employed as the base material in the broad sense and intend to include suitable waxes 'molded bodies which are the subject of this apand. all such equivalent substances. 0 plicatlon are exceedingly light in weight, from Whengranular spumiform material of this .9 to 1.5 lbs. r cubic foot in density, and the kind containing asphalt is poured. while hot vidual particles of the granular material are into an insulation compartmen' t' on gently com- 1 very fragile for the essential "characteristic of eased, it will be round that the m t the material is that particles thereof consist of e r by reason of the asphalt on their exa one or more hollow cells with very thin shells. terior surfaces, and form upon solidification of a It 'wil be obvious therefore, that this material the asphalt in cooling at semi-solid structure jo cannot be successfully mixed with bonding subwhich, while it has'very little strength, is sufiistances like asphalt in the same way that rock ciently strong to absolutel I gm; glitlm or similar strong material is mixed. A wholly the particlesin H By tbismethdlfierent technique must be employed from that ou-we"5i-6d*uiitlr'veEei'c"lfnt molded body or o 1 used in bonding other types of granular material. heat insulation which a permanently tree from i This is further emphasized by the fact that our settling, and is very light inweight, and consel: finished molded vbodies herein described gen- .quently has high value. The density i ell-m welgnalllitueasrl-om 1.5to8lbs.per ofsuchamoldedbodymaybeaslowasldlbs.

percuit; Ehemoctdsirablepmcedureintormor s-mm ing such a molded body is to pour the intumesced granules directly from the intumescing device, where they have been heated, into the compartment to be filled. In this molded body the asphalt binder is present in an amount far less than that required to fill the voids between the granules, thus making a body with a high percentage of voids and therefore a' good insulator of heat.

We may also bond together the granules of spumiform material which do not have pitch as one of their body ingredients. Such solidified intumescent materials, as alkaline silicate; sodium tetraborate; or a compositionfb falkaline oxide, boric oxide, and silicon dioxide, having a spumiform structure, are described in detail together with methods for their manufacture in either our issued patent or our copending application above referred to. Briefly, they are made in about the same way as the material containing pitch exceptthat pitch is not added in their manufacture. In bonding together such granular materials, pitch is introduced in a finely divided form into a body of the hot spumiform particles preferably by spraying hot asphalt or coal tar of high penetration (100 or 250), or a thin solution of pitch in carbon tetrachloride or other suitable solvent, or an emulsion of pitch in water,-and the batch is tumbled to assure uniform distribution of the molten asphalt. If such a solution or emulsion is employed, the carbon tetrachloride or the water readily evaporates leaving a thin coating of pitch on all the granules. Alternatively, the pitch may be added to'the body of hot spumif ranules in the for a ia w ere the pitch employe has a sufiiciently igh melting point to permit of finely dividing it.- In any case, the body of hot h coe form granules then poured into the insulation compa ment to be filled and allowed to cool, whereupon the pitch solidifies and binds all the particles together into a molded body of heat insulation as heretofore described. We furthermore find it advantageous to spray asphalt or apply pitch in one of the above described forms to the exteriors of spumiform granules which also have pitch uniformly distributed throughout each granule and which would normally bond without additional pitch. This is becausea'g'iven quantity of pitch is'more efiective in bonding if added to the exteriors of the granules on account of -less being evaporated during the desiccating and intumescing steps and also because of the fact that-the pitch is on the exteriors of the particles where it is all available for bonding; By this additional coating of the exteriors of the granules, then, a stronger bond is provided by use of very little more pitch. Naturally the granules having pitch through and through are preferred because they provide a more water-repellent structure. We may employ an extension of the above-described methods in making molded bodies having considerable strength: Spumiform granules of any intumescent composition, and made by any of the methods, heretofore mentioned and having pitch on their "exteriors available for bonding are, while hot, compressed into a molding form of desired shape: When the compressed body cools, the plastic pitch solidifies,acting as a binder for the spumiform particles, and making a solidly bonded body which, however,- retains Y in some measure the desirable flexible qualities of pitch. The compressing operation may be done by means of a press with pistons forcing the' spumiform materialintothe mold;- or'by rolling it in;

is preferably performed by first pressing the material into the form and then, when the shape of the form permits, rolling the surface. This whole operation is preferably done under conditions which maintain the block of molded material hot. Compression of the material is essential in securing a strong well-bonded body that is intended to be removed from the form and to withstand handling. The density of the finished molded body is dependent upon the degree of compression but is generally made from 4 to 8 lbs. per cu. ft. 1

Because when force is applied to any body to bend it, the greatest stress comes on the surface layer, we prefer to provide additional strength in this layer. This is done by providing to the molded body above described essentially a surface coat of pitch. After the solid molded body has been formed it is impregnated by either spraying or dipping in hot asphalt or coal tar pitch until the pitch has penetrated a little way into the interior of the absorptive surface of the molded body and has formed a definite surface shell in which the pitch substantially fills the voidsbetween the bonded particles. Diatomaceous earth. gyp um, or similar substance may advantageously be blown onto this surface where it sticks and helps to make a smooth hard finish when the pitch cools. I

An alternative method of bonding together spumiform particles through a bond-of pitch is as follows. In the preparation of the spumiform granules, the intumescing step is 'stopped' before all the water has been evaporated from the intumescent material. A partially expanded granular spumiform material results whichis able to further expand upon renewed heating: For the purpose of this method we prefer to leave about 4 to-5% water remaining in the partially expanded particles. The intumescent material may be any of those previously mentioned and the granules may have pitch included within them or have pitch applied only on their exterior surfaces as above described. We place a sufiiclent quantity of these partially expanded granules in a molding form, preferably compressing them in to compactly fill the form. The molding form is then closed loosely so as to confine the solid contents and is subjected to a temperature sufficient to-complete the intumescence of the contained hydrous material and to melt the pitch. Generally a temperature of about 650 F. is used and is continued until desiccation of the contained material is complete- The molded body is allowed to cool in the form and is then removed therefrom. It will be found to be a very solid, strongly bonded material. This molded material should be distinguished from that which is described in our copending application and which results if granules containing more water are used and if the temperature is carried high enough to cause the softenedintumescing granules to break through the surface asphalt layers and unite. The material described in the present application is not united in this manner; it is composed of .pitchy granules bonded together by the pitch existing on the surfaces of the granules, and the intumescence of the granules simply provides a convenient method of securing compression of the granules while the heat required for intumescence melts the pitch on the granule exteriors and permits the granules to bestuck together. The continued heating of the molded body then results in vaporization of the-more I06. COMPOSITIONS,

COATING OR PLASTIC.

Cross Reference Examiner volatile pitch components leaving a hard, strong pitch to serve as a bond. An alternative method is to compress into a form a body-of completely expanded spumiform granules ofany of the compositions, and made by any of the methods aforementioned, and which have pitch on their exteriors, or a mixture ofsuch granules and finely divided solid pitch of ahigh melting point. In any case, the form 40 and contents are heated to melt the pitch and cause it to distribute over the immediately near granule surfaces and to bond adjacent granules together. Upon continued heating, the more volatile-components of the pitch are vaporized and escape, leaving a hard, strong, very high melting point pitch as a bond. In the bonding processes above-described, except the last, the action has included the step of solidifying a non-solid binder by cooling it. In the method last described, another way of solidifying entered in, namely, solidification of a non-solid binder by evaporation of the volatile constituents. We will now describe other examples of this type of solidification by evaporation 2 to effect bonding of our spumiform granules.

Granular spumiform material is made as above described, using as intumescent substance either alkaline silicate alone, or sodium tetraborate alone, or the composition containing alkaline oxide, boric oxide, and silicon dioxide, or any of these materials together with pitch as above described. This granular spumiform material is mixed with a non-solid binder, compressed into a molding form of the desired shape and dried, either in or out of the form, until the binder has solidified. A very satisfactory binder consists of a mixture of 10 pounds of a 4% water solution of sodium al enate with Y; poun o a Wm'water. The asphalt emulsion 1s preierabTy a very staBle one that can withstand the extreme dilution required. Instead of sodium algenate in the formula, any water soluble algenate may be substituted.

28 ounces of inder is used to every pound of the su orm ar 10 The spumiform mamixed together and mixing is continued until substantially all the particles are coated with the binder. The moist mixture is then compressed into a form, and when the shape permi s, a ional ma cm] is rolled into the surface. Inasmuch as the granular material weighs only .9 to 1.5 pounds per cubic foot and it is ordinarily desired to produce a block weighing 6 to 8 pounds per cubic foot, it will be noted that a considerable compression is required in this operation. During compression, many of the granules which are composites of several bubbles are broken down into smaller units while still retaining their bubbled shape. The compressed moist block is, whenever possible, given a surface spray coat of the same solution which is employed as binder. It is then fired to dr and o if the binder. In firing,

' e entirely enclosed; for example, a block as thin as one inch is after compression sufiiciently strong to be handled and go through the drier on edge with the large flat sides of the form removed and only a rim around the thin edge of the block to protect it. Thus the maximum surface area of the block is exposed and drying is veryrapid. The temperature at which drying is conducted is preferably 500 F. and at this temperature a one inch 0 dries in about 1% hours. Other bonding solutions may be employed. For

example, an algenate without the addition of asphalt emulsion makes a good bond. 26 ounces of a 4% solution of sodium algenate is mixed with 1 pound of spumiform granules. The drying operation is the same as when asphalt is present. 2 I

Solutions 'of-mmay' also be used as binders.

22 ounces of a 2 -to 4% water solution 0 arabi may be employed to bond 1 pound of iform granules. With this binder, drying is qa done at 350 -1 and a one inch thick block dries in about 1 hour.

These insulating blocks made by bonding together spumiform granules by one of the hinders and in the manner just described may be as made strong .enough to handle, saw, and nail through and yet weigh only 6 to 8 pounds per cubic foot.v When made with a binder of algenate and asphalt emulsion theyare suitable for continued use -at temperatures up to 800 F. Q0

.In all the .molded bodies described herein, we prefer to employ binder in an amount less than that sufiicient to fill the voids between the spumiform particles being bonded, except in surface layers as previously. indicated; and in this man- 5 ner we secure C very .lightceflicient insulatin bodies.

It is desirable to call attention to the notable advantages from the standpoint of heat insulation of the internal structure of the molded 30 bodies made by bonding together spumiform granules of the character of those employed in our invention. These granules are called spumiform because they are similar in form to little bits of solidified foam. Some are so small that they consist of only a single bubble just as a piece of foam small enough will consist of a single bubble. This bubbled character, accompanied by thin bubble walls, is what we mean to indicate when we apply the term spumiform to all the particles whether they consist of one hollow bubble or many bubbles joined. The thin walls, which are generally of much less thickness than the enclosed bubble spaces, permit deflection under pressure and thus cause a body of the spumia form granules to be compressible and resilient.

The problem of heat insulation is essentially one of forming the greatest number of closed air cells of the smallest volume per cell, while using the minimum amount of solid material in the 50 cell walls. It is well known that a sphere requires the minimum amount of surface area to enclose a given volume and the contact surface between spheres is smaller than for any other shape. Thus a blockbuilt up by bonding hollow 56 cells having spherical enclosing surfaces is capable of a greater insulating value or lower conductivity than a body made by using cells of any other shape. Because of the bubbled character of our spumiform granules, therefore, they are 60 best suited to be bonded together to form a light, strong block of maximum insulation value, and the tested efliciency of the molded bodies described herein amply confirms this analysis.

In using the term intumescent substance 65 herein, we mean to describe a substance of the class of those disclosed which under proper circumstances is capable of intumescence, but do not mean to imply that an intumescent substance is always capable of intumescence; for a solidified 7 intumescent substance which is completely desiccated, or anhydrous, can no longer intumesce.

It is to be understood that various changes and modifications in the details of compositions and 75 u. pitch on their exterior surfaces.

2. The method of making a molded body which includes the steps of forming a uniform mixture of pitch in a hydrous solution of an intumescent substance, partially desiccating said mixture to go form a solid containing water, comminuting said solid, heating said comminuted material to form intumescent spumiform particles retaining a small amount of water and having pitch on their exterior surfaces, compressing into a molding 25 form a body-of said spumiform particles, and

heating the form and contents to melt the pitch on their exterior surfaces and to cause-said pa ticles to further intumesce and press tightly together, in such manner that they become bonded through the surface layers of pitch.

3. The method of making a molded body which comprises introducing pitch in a finely divided form into a body of spumiform granules of a solidified composition containing alkaline oxide, horic oxide, and silicon dioxide, the pitch being of an amount less than that required to fill the voids between the granules, compressing said body of granules while hot, and solidifying said pitch.

4. The method of making a molded body which includes confining, in a molding form, a body of hydrous spumiform granules of a solidified composition containing alkaline oxide, boric oxide, and silicon dioxide, said granules including pitch on their exterior surfaces, and heating the form and contents to melt said pitch and to cause said granules to further intumesce and press tightly together, in such manner that they become bonded through the pitch on their exterior surfaces.

ALBERT A. FOWLER. RUSSELL M. OTIS. 

